The objectives of this grant renewal application are clinical and basic on the clinical level (1) is to clarify the interaction of the many factors involved in the production and severity of acute and cicatricial retrolental fibroplasia (RLF) in the premature population by multiple logistic risk analysis, (2) to investigate in selected "high risk" prematures the role of arterial oxygen tension in the genesis of acute, proliferative RLF, and (3) on the more basic level, to explore a promising animal model for the production of cicatricial RLF.